The present invention relates to drug delivery devices, and particularly to such devices which deliver the drug via micro-needles and/or iontophoretically.
The conventional way of transdermal drug delivery, namely by hypodermic syringe injection, is very unpleasant and painful, and therefore many alternative ways of drug delivery have been developed. The transdermal patch delivers the drug by diffusion, utilizing merely a concentration gradient as a driving force, but this technique is not very effective with respect to large-molecule drugs, such as proteins and peptides, or drugs which otherwise do not have the proper physiochemical properties for diffusion through the skin.
In recent years, micro-needle type drug delivery devices have been developed for increasing the permeability of the skin by micro-needles having a length of up to about 150 microns, sufficiently short so as not to engage the nerve endings but long enough to penetrate the cornified outer body surface layer. They can be produced from a variety of materials, such as silicon, metal and plastic polymers, in many different sizes and shapes. Examples of such micro-needle type drug delivery devices are described in U.S. Pat. Nos. 3,964,482, 6,611,707, 6,656,147 and 6,558,361, the contents of which are incorporated herein by reference.
An object of the present invention is to provide a drug delivery device of the micro-needle type having a number of advantages, as will be described more particularly below.